1. Field of the Invention
This invention relates to a supercritical refrigerating system suitable for a supercritical refrigerating cycle (hereinafter referred to as CO.sub.2 cycle) using carbon dioxide (CO.sub.2) as refrigerant, in which a pressure inside a radiator exceeds a supercritical pressure.
2. Description of the Related Art
As disclosed in WO 90/07683, to exhibit a specific refrigerating capacity in a CO.sub.2 cycle, the CO.sub.2 cycle needs to maintain a high-pressure side (radiator side) pressure equal to or more than a specific pressure.
In an automotive refrigerating cycle using fleon as refrigerant, the refrigerating capacity is controlled by operating and stopping a compressor via an electromagnetic clutch. In the CO.sub.2 cycle, however, when the refrigerating capacity is controlled only by operating and stopping the compressor, the high-pressure side pressure, which needs to be kept at the specific pressure or more as described above, may decrease during the time when the compressor is stopped. In this case, it becomes difficult to exhibit a sufficient refrigerating capacity immediately after the compressor is restarted.
To solve this problem, it is conceivable that the refrigerating capacity is controlled by changing a discharge capacity of a variable capacity type compressor, without stopping the compressor. However, this method requires a complicated structure of the compressor and a control amplifier for controlling the compressor, resulting in increased manufacturing cost.